The present invention relates to a battery pack, and to a method of monitoring removal of a secondary battery in the battery pack.
A battery pack has been heretofore used for various portable apparatuses such as a mobile phone, a digital still camera, a portable game machine, a notebook personal computer, and an electric power tool. Currently, applications thereof are not limited thereto, and the battery pack has been increasingly used in the fields necessitating a higher output and a higher capacity such as an electric assist bicycle, an electric vehicle, and a home electric storage device.
Examples of secondary batteries built into a battery pack include a lithium ion secondary battery, which is currently one of the most-mainly-used secondary batteries therefor. The lithium ion secondary battery has multiple characteristics as follows. That is, the lithium ion secondary battery is repeatedly usable by charging, has a high voltage output, has high energy density, has little self-discharge, and has a long life. Therefore, the lithium ion secondary battery is used in an extremely-broad range. However, since the lithium ion secondary contains a combustible material, adequate care needs to be exercised in handling thereof. Further, for addressing needs of apparatuses such as a higher output and a higher capacity, the number of cases in which secondary batteries (single cells) are multiply-series-connected or multiply-parallel-connected, and are used in a state of a battery pack (assembled battery), and therefore, more proper handling thereof is desired. Furthermore, in order to determine whether or not a battery pack mounted on an apparatus is safely usable for the apparatus, many battery certification systems for acting certification between an apparatus and a battery pack have been introduced. Accordingly, usage of an inappropriate battery pack is allowed to be restricted by various certification methods including whether or not an appropriate battery pack is used and whether or not an appropriate protection circuit is included.
There is concern that what we call an altered battery pack is manufactured and distributed by disassembling a spent battery pack, taking out a secondary battery, and building the secondary battery into other battery pack. In such an altered battery pack, undesired over-charge, undesired over-discharge, and/or the like may occur by building in an inappropriate secondary battery, and therefore, a safety issue easily occurs. Therefore, it is strongly desired to appropriately suppress manufacture and distribution of the altered battery pack by disqualifying such an altered battery pack from certification and/or substantially disabling a function of the altered battery pack.
As such a battery pack aimed at preventing alteration, a battery pack provided with an IC tag in which predetermined information is recorded is known from, for example, Japanese Unexamined Patent Application Publication No. 2006-324075. Further, a battery pack in which a detachment recognition tape having a detachment recognition function with which a fact that a battery has been separated from a package case is certified is adhered to a region from the battery to a member adjacent thereto is known from Japanese Unexamined Patent Application Publication No. 2005-353518.